Table 2.

Key parameters and their origin ^(a)

Parameter	Previous estimates (b)	Intrinsic (c)	apparent(d)
pKa(BH)I	(−2; 7) (e), (7 to 10) (l), 9 (m)	5.00	5.54
pKa(BH)X		7.20	7.47
pKa(PH)I	−1 (f), 2 (g)	−1.00	−1.03
pKa(PH)III		−1.00	−1.59
pKa(PH)X	−4 (f), 0 (g)	−1.00	−1.44
pKa(EH)I	9.4 (h), 10 (i)	9.00	9.42
ΔI ([a− a3] → [a a3−])I		−2.50 (i)	−2.71
ΔI ([a− a3] → [a a3−])III	−1 (j), −4 (k)	−5.54	−5.63

^aThe pK_a values are given in pK_a units whereas the reduction potential is in kcal/mol

^bPrevious estimates from the literature.

^cEvaluated by the PDLD/S-LRA method where the interactions with the protein ioniozable groups in the active space ( those included in the state diagrams ) are not included, except the Heme(Fe) ··· OH⁻ interaction and the interaction between Arg 481 and Prd, which are included explicitly.

^dIncludes V_QQ interaction with other residues (excluding the interactions that were already considered in ^(c)). The calculations were done with ε′=60.

^esee text and ref[16].

^fThe pK_a value of Prd is evaluated by PDLD/S-LRA where the effect of Arg 481 is included explicitly.

^gEvaluated by the PDLD/S-LRA where the effect of Arg481 is included implicitly with Eq. 7 and ε′=60.

^hTaken from the most quoted experimental estimate (ref[10])

ⁱObtained by PDLD/S-LRA calculations[20]

^jTaken from the estimate of ref[57]

^kEstimated by PDLD/S-LRA calculations

^lBased on an assumed effect of the iron bound to OH⁻ and the reduction potential of the heme.

^mTaken from the estimate of ref[55]